Cyanocobalamin is an especially common vitamer of the vitamin B12 family. It is the most famous vitamer of the family, because it is chemically the most air-stable, and it is the easiest to crystallize and therefore easiest to purify after it is produced by bacterial fermentation. A form of B12 called hydroxocobalamin is produced by bacteria, and then changed to cyanocobalamin in the process of being purified in activated charcoal columns after being separated from the bacterial cultures. Cyanide is naturally present in activated charcoal, and hydroxocobalamin, which has great affinity for cyanide, picks it up and is changed to cyanocobalamin. Thus, the cyanocobalamin form of B12 is the most widespread in the food industry.